Which lines of A, B, and C are perpendicular?

a is perpendicular to both b and c; the product of the slopes a and b or a and c is -1

Step-by-step explanation:

perpendicular slopes multiplied by each other would be -1

-1/3 * 3 for a and both other lines is -1

that means a is perpendicular to both b and c

= 5

step-by-step explanation:

to find the 15th term substitute n = 15 into the nth term formula

= (- 3 × 15 ) + 50 = - 45 + 50 = 5